Mum is not quite ready to leave rehab, but they are preparing us to get her out. What do we do?

Mum had a severe infection that affected her heart and eye. Lost vision in the eye and needs vitral valve replacement. She is 91, so no surgery; but they have her on IV antibiotic for 6 weeks. Before proper diagnosis and proper treatment, she was in hospital for about 3 weeks. Needless to say she is VERY weak and fatigues quickly. She was in independent living and wants to return there. She has 3 more weeks of IV and then re-eval for what next, but she is slowly progressing to care for self. Not enough strength to walk and has rehab for OT and PT. This is a rehab facility and it she shows progress, they want her out. If she is plateauing, they want her out. The dilemma is where does she go? Assisted still requires paying for each need (ala carte)! Or she goes home with the same need of ala carte care. She is not able to do/remember all steps and hope she will get there in the about 2 weeks they are giving her. What are the best supportive info to add to an appeal with insurance and the OT/PT. They seem to have the final say. Doctor has not disputed their recommendation in 10 years!